<canvas width="600" height="400"></canvas>
<script>
var tela = document.querySelector("canvas");
var pincel = tela.getContext('2d');
pincel.fillStyle = 'lightgrey';
pincel.fillRect(0, 0, 600, 400);
pincel.fillStyle = 'green';
pincel.fillRect(100, 50, 350, 300);
pincel.fillStyle = 'black';
pincel.fillRect(150, 100, 90, 90);
pincel.fillStyle = 'black';
pincel.fillRect(300,100,90,90);
pincel.fillStyle = 'black';
pincel.fillRect(240, 190, 70, 100);
pincel.fillStyle = 'black'; pincel.fillRect(310, 240, 40, 110);
pincel.fillStyle = 'black'; pincel.fillRect(200, 240, 40, 110);